Definitely this is not a perfect solution, but it's working fine for me on desktop/web platforms. The point is that on mobile platforms (Android/iOS) the itemId is sightly different, and the URL I construct is not valid.

On desktop, the itemId is composed using base64 (alphanumeric, '+', '/') while mobile one contains '-' and '_' instead of '/' and '+'

displayMessageForm will open an existing message from the itemId for desktop and web, but it is not supported in Outlook for iOS or Outlook for Android.
– Outlook Add-ins Team - MSFTDec 13 '18 at 23:16

Thanks for pointing that out, I missed the platform they are targetting.
– Brian ClinkDec 14 '18 at 15:46

I want to use the URL to open the message in Outlook Web App. For instance, using Graph API I can get a message and then use its "weblink" property (docs.microsoft.com/en-us/graph/api/resources/…). I just wonder if there's another way to get that link faster, using the Outlook API itself
– Paolo RaezDec 17 '18 at 8:33

1 Answer
1

Currently, constructing a URL from the itemId, you requested, is not a part of the product. We track Outlook add-in feature requests on our user-voice page. Please add your request there. Feature requests on user-voice are considered when we go through our planning process.